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Homework Help: Arithmetic Progression

  1. May 29, 2015 #1
    1. The problem statement, all variables and given/known data
    The first term of an a.p is -8, the ratio of the 7th term to the 9th term is 5:8. what is the common difference of the progression?

    2. Relevant equations

    3. The attempt at a solution
    I've tried... it confuses me. Can anyone give me some hints or tips...?
  2. jcsd
  3. May 29, 2015 #2


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    Staff Emeritus
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    Homework Helper
    Gold Member

    Hello osirvics. Welcome to PF !

    In the future, you need to show your attempt at a solution.

    Do you know a general formula for the nth term in an arithmetic progression ? What is that formula?
  4. May 29, 2015 #3
    Okay, thanks.
    Yes, tn = a + (n – 1) d.
    but i don't know how to implement it. this statement "the ratio of the 7th term to the 9th term is 5:8" is confusing me.
  5. May 29, 2015 #4


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    Staff: Mentor

    Thread has been locked for your not showing any effort. Please start a new thread and fill out your Attempt at a Solution part of the HH Template. Thank you.
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